By default, SSDM tool does not prompt for the date filter in the GUI. Askfilter=1 under [General] is used.
You would like to use only messages that are dated on or after filter. For this reason, the second radio button is selected under Mail dates filter.
However, when the second radio button is selected, the next button gets grayed out and you are not able to select Next.
If you select the third radio button under Mail dates which is Migrate only messages that are dated on or before, the Next button becomes available.
1- Remove AskFilter=1 under [General] of gwdtapp.ini file. This is the INI file of the SSDM tool
2- Find [Filter] Section
3- Add FirstMailDate=mm/dd/yyyy
4- Save INI file
Waiting for a fix in a future release of Migrator for GroupWise.